Added missing autocommit call.

[matej-io]

Added missing autocommit call to MySQL wrapper.

Without this you can't start transactions which can be rolled back, which I think it is important for integrity of the database especially on the server side.

[RockfordWei]

@matejukmar Thanks for the PR. Would you please add the corresponding test script as well? Also please note that most future of end users would probably use CRUD as well, so would you like to make some comments for this call in CRUD applications? @kjessup @iamjono